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Transcript
BRIDGEND ASTRONOMICAL SOCIETY NEWSLETTER
VISIT TO NORMAN LOCKYER OBSERVATORY IN SIDMOUTH AUGUST 8th 2015
Jon Laver is organising a Society visit to the famous Norman Lockyer
Observatory in Sidmouth, Devon where we will be given a talk and a
tour of the observatory and telescopes. The South West Astronomy Fair
is being held at the NLO on that date and there will be lots of special
events going on. Speakers include Allan Chapman and Richard Fleet.
More information at: http://www.southwestastrofair.com/
SKYLUX LINSEN TELESKOP REFRACTOR TELESCOPE FOR SALE
This telescope is being sold by Gareth Aston who lives in Litchard, Bridgend
and comes with a sturdy tripod. His e-mail address is [email protected]
and you will have to negotiate the price. The telescope is F=700, D = 70 with 20mm,
12mm and 4mm eyepieces.
PRESS RELEASE
Bridgend Astronomical Society starts its 34th season of meetings with two free events for the
interested public.
On Saturday 19th September, BAS are holding an Open Day in Pyle Church Hall, 1400 – 1700 hrs.
Exhibition, Ask the Expert, Telescope Workshop, Introduction to Astronomy illustrated talk, etc.,
refreshments available. The workshop is free to anyone with an astronomical telescope that they
need help or advice with. All astronomically interested members of the public are welcome, no
experience or equipment necessary.
BAS are also holding a Public Observing Session in the car park of Parc Slip. 2100 – 2300 hrs. This is
nominally for Friday 18th September, but of course is weather dependent. Saturday 19th is the first
alternative, followed by 25th & 26th. The society’s telescope will be there plus several members with
their own telescopes. Members of the public are encouraged to bring their own telescopes for which
help will be available if required. A Sky Tour is also planned. See website.
BAS meets on the second Friday of the month at Pyle Church Hall at 1930 hrs. The season of talks
starts off with “Solar Eclipses” on September 11th. In addition to the main talk, there are also
updates, items on sky news, etc.
CHRISTMAS DINNER
We will return to the Fountain Inn at Aberkenfig which is under new management. Details to
be confirmed in the autumn.
SEPT 11 Solar Eclipses by Margaret Collins of Swansea Astronomical Society
OCT 9 TBA by Dr Bob Owens of National Museum of Wales
NOV 13 The Hale Telescope by Dr Rhodri Evans of Cardiff University
DEC 11 Transient Astronomy with Gravitational Waves by Dr Stephen Fairhurst of Cardiff
University
2016
JAN 8 A 3D Tour of our Solar System and Beyond by Emma Wride of the University of South
Wales
FEB 12 Extra Dimensions and the Brane World Scenario by Dr Ivonne Zavala of Swansea
University
MAR 11 Studying the Atmospheres of Extra-Solar Planets by Professor Matt Griffin of
Cardiff University
APRIL 8 The Faulkes Telescope Project By Dr Fraser Lewis of The Faulkes Telescope Project
and National Schools Observatory
APRIL 24 AGM
MAY 13 The Gaia Satellite by Dr Sarah Roberts of the University of South Wales
The Night Sky August 2015
Compiled by Ian Morison
Cambridge University Press has recently published two books by the author. An
Amateurs Guide to Observing and Imaging the Heavens is a handbook aimed to
bridge the gap between the beginner's books on amateur astronomy and the books
which cover a single topic in great detail. Stephen James O'Meara and Damian Peach
have both given it excellent reviews. 'A Journey through the Universe' covering our
current understanding of the Universe (up to June last year) was published on the 25th
of September. Martin Rees has written a very nice review of it.
Image of the Month
Charon imaged by New Horizons
Charon
Image: NASA,John Hopkins Univ./AP, Southwest Research Institute.
Of all the images so far sent back by New Horizons, this is the one I like best. Charon was
discovered by Jim Christy in 1978 and this allowed the mass of Pluto to be calculated - it was far
smaller and less massive that had been thought when it was discovered and, to be honest, if Pluto
were discovered now it would never be classified as a planet. I was a little sad though when it
was demoted and would have liked it to have been allowed to stay as an 'honorary
planet'. Charon is 1,200 km across - half the diameter of Pluto and about 1/10th the size of
Earth. Its terrain is surprisingly youthful and very varied including a 1,000 km swath of cliffs and
troughs seen below the centre of the image and, along the upper right edge, a 7 to 9 km deep
canyon. The enigmatic dark polar region has been dubbed 'Mordor'!
Highlights of the Month
August - Find the globular cluster in Hercules and spot the
"Double-double" in Lyra
Use binoculars to find the globular cluster M13 in Hercules and the "Double-double" in Lyra
Image: Stellarium/IM
There are two very nice objects to spot with binoculars high in the sky after dark this
month. Two thirds of the way up the right hand side of the 4 stars that make up the
"keystone" in the constellation Hercules is M13, the best globular cluster visible in the
northern sky. The 15 minute exposure image on right was taken by the author using a
127 mm APO refractor and SBIG 8.3 megapixel CCD camera.
Just to the left of the bright star Vega in Lyra is the multiple star system Epsilon Lyrae
often called the double-double. With binoculars a binary star is seen but, when observed
with a telescope, each of these two stars is revealed to be a double star - hence the
name!
August - A good month to observe Neptune with a small
telescope.
Neptune in Aquarius
Image: Stellarium/IM
Neptune comes into opposition - when it is nearest the Earth - on the 31st of August, so
will be seen well both this month and next. Its magnitude is +7.9 so Neptune, with a
disk just 3.7 arc seconds across, is easily spotted in binoculars lying in the constellation
Aquarius as shown on the chart. It rises to an elevation of ~27 degrees when due
south. Given a telescope of 8 inches or greater aperture and a dark transparent night it
should even be possible to spot its moon Triton. (This is my objective around the end of
the month!) It lies very close to the 7th magnitude star HIP 111910 and, on the 5th of
September, will lie directly above it.
August 7th after sunset: Jupiter and Mercury close to
Regulus in Leo.
Jupiter, Mercury close to Regulus in Leo.
Image: Ian Morison
One of the last chances to see Jupiter this apparition in on the 7th. Given clear skies
and a low western horizon it should be possible to spot Jupiter and Mercury within a one
degree diameter circle with the star Regulus in Leo.
Both planets will be then nearly fully lit, but Jupiter's 31 arc second disk will appear
significantly less bright than Mercury's disk, some six times smaller.
August 8th - 45 minutes before sunrise: Mars below Castor
and Pollux in Gemini
Mars below Castor and Pollux
Image: Stellarium/IM
Before sunrise on the 8th of the month there is a chance of spotting Mars, with a
magnitude of +1.7 and angular diameter of 3.7 arc seconds, at the start of its new
apparition lying, in Gemini below Castor and Pollux.
The good news is that when Mars it at its closest in May next year, its angular diameter
will reach 18.6 arc seconds in comparison to the meagre 14 arc seconds peak during the
last two apparitions. Sadly it will be then be at a rather low elevation.
The mornings of August 12th and 13th and 14th: midnight
to dawn - look out for the Perseid meteor shower.
A Perseid meteor
If clear, these mornings should give us a chance of observing the Perseid meteor shower
- produced by debris from the comet Swift-Tuttle. The peak of the shower is after
sunrise on the morning of the 13th so the early morning of the 13th August will give us
the best chance, if clear, of viewing the shower, but the peak is quite broad and so its
well worth observing on the nights before and after. Most meteors are seen looking
about 50 degrees from the "radiant" which lies between Perseus and Cassiopeia. The
great thing about this year is that, with New Moon on the 14th, there will be no
moonlight to hinder our view in the days around the peak. Under cloudless skies and
from a dark location observers might expect to see 50 to 70 meteors an hour near the
peak (the last hours of darkness on the morning of the 13th).
Looking East at ~1am on the morning of the 13th August
Image: Stellarium/IM
August 22nd - one hour after sunset: Saturn close to a first
quarter Moon - and a lunar occultation of Theta Librae.
Saturn close to a first quarter Moon..
Image: Stellarium/IM
Looking west after sunset, Saturn, in Libra, will be seen close to a first quarter Moon. A
good horizon in the South South-west will be needed. Whilst producing the diagram
using the Stellarium program, I spotted the, 4th magnitude, star Theta Librae very close
to the Moon's dark limb. It should be seen to disappear behind the limb around 21:41
BST.
Theta Librae occulted by the Moon.
August 7th and 23rd: The Straight Wall
Location of the Straight Wall: IM.
The
Straight
Wall
The Straight Wall is best observed either 1 or 2 days after First Quarter (23rd August:
evening best) or a day or so before Third Quarter (evening of the 7th August best). To
honest, it is not really a wall but a gentle scarp - as Sir Patrick has said "Neither is it a
wall nor is it straight!".
The Straight Wall at Sunrise and Sunset.
A Messier Object imaged with the Faulkes Telescope:
galaxy NGC 1365.
NGC1365
Image:Nik
Faulkes Telescope.
Szymanik
Galaxy
NGC
1365,
imaged
by
Nik
Szymanek.
This image was taken using the Faulkes Telescope by Nik Szymanek - one of the UK's
leading astro-photographers.
NGC1365 is also known as the Great Barred Spiral
Galaxy and lies at a distance of 56 million light years. It is one of the most perfect
barred spirals with a straight bar and two very prominent spiral arms. Closer to the
centre there is also a second spiral structure. The galaxy is an excellent "laboratory" for
astronomers to study how galaxies form and evolve.
Learn more about the Faulkes Telescopes and how schools can use them: Faulkes
Telescope"
Observe the International Space Station
Use the link below to find when the space station will be visible in the next few days. In
general, the space station can be seen either in the hour or so before dawn or the hour
or so after sunset - this is because it is dark and yet the Sun is not too far below the
horizon so that it can light up the space station. As the orbit only just gets up the the
latitude of the UK it will usually be seen to the south, and is only visible for a minute or
so at each sighting. Note that as it is in low-earth orbit the sighting details vary quite
considerably across the UK. The NASA website linked to below gives details for several
cities in the UK. (Across the world too for foreign visitors to this web page.)
Note: I observed the ISS three times recently and was amazed as to how bright it has
become.
Find details of sighting possibilities from your location from: Location Index
See where the space station is now: Current Position
The Moon
The Moon at 3rd Quarter. Image, by Ian Morison, taken with a 150mm MaksutovNewtonian and Canon G7.
Just below the crater Plato seen near the top of the image is the mountain "Mons Piton". It casts
a long shadow across the maria from which one can calculate its height - about 6800ft or 2250m.
`
new moon
first quarter
full moon
last quarte
August 14th
August 22nd
August 29th
August 7th
The Planets
Jupiter
Jupiter passes behind the Sun on August 26th so can only be observed during twilight
at the very beginning of the month low in the west after sunset.
Venus passed 6
degrees below Jupiter on July 31st so will be close for the first few days of the month but
becoming progressively more difficult to observe. It was good to observe the two close
together, still reasonably high in the sky during twilight, during the first part of July.
Saturn
Saturn is the only bright planet visible outside twilight this month. It lies in Libra near
the wide double star Alpha Librae falling in brightness a little from +0.4 to +0.5
magnitudes during the month. It ceases its retrograde motion westwards in the sky on
August 2nd and so begins to move eastwards back towards Scorpius. One hour after
sunset it will lie just 20 degrees above the horizon so the atmosphere will limit the view
of its 17 arc second disk but the ring system, now 24 degrees open, should still show
nicely along with Titan, its largest satellite. Saturn will be 90 degrees east of the Sun
(eastern quadrature) on August 21st so the globe's shadow on the rings is at its
maximum extent giving a three-dimensional feel to our view of this, most beautiful,
planet.
Mercury
Mercury . This month Mercury returns to the twilight sky before sunset increasing in
brightness from +1.2 to +0.1 during the month as it rises a little higher in the western
sky.
Mars
A Hubble Space Telescope image of Mars.
Jim Bell et al. AURA / STScI / Nasa
Mars. As August begins, Mars, shining at magnitude +1.7, rises about 70 minutes
before the Sun. This increases to 2 hours by month's end with its brightness virtually
unchanged at +1.8 magnitudes. On August 8th, at an elevation of just 5 degrees, it will
lie below Castor and Pollux in Gemini around 45 minutes before sunrise whilst on the
mornings of the 20th and 21st it will lie close the M44, the Beehive Cluster in Cancer.
Venus
Venus, rises at sunrise on the 18th of August, but 55 minutes before the Sun a week
later and about one hour 30 minutes by month's end. As it does so, its brightness
brightens from -4.1 to -4.5 magnitudes and its angular size reduces slightly from 58 to
52 arc seconds whilst the percentage illuminated area (phase) of the planet increases
from 1 to 9%. So close to the Sun, it is not safe to observe after sunrise.
The Stars
The mid evening August Sky
The August Sky in the south - mid evening.
Now that the evenings are drawing in, the night sky gets darker earlier so encouraging
one to go out to observe.
This map shows the constellations seen towards the south at about 10pm BST in mid
August. High overhead towards the north (not shown on the chart) lies Ursa Major. As
one moves southwards one first crosses the constellation Hercules with its magnificent
globular cluster, M13, and then across the large but not prominent constellation
Ophiucus until, low above the southern horizon lie Sagittarius and Scorpio. To the right
of Hercules lie the arc of stars making up Corona Borealis and then Bootes with its bright
star Arcturus. Rising in the east is the beautiful region of the Milky Way containing both
Cygnus and Lyra. Below is the constellation of Aquila, the Eagle. The three bright stars
Deneb (in Cygnus), Vega (in Lyra) and Altair (in Aquila) make up the "Summer
Triangle".
The constellation Ursa Major
Ursa Major
The stars of the Plough, shown linked by the thicker lines in the chart above, form one
of the most recognised star patterns in the sky. Also called the Big Dipper, after the
soup ladles used by farmer's wives in America to serve soup to the farm workers at
lunchtime, it forms part of the Great Bear constellation - not quite so easy to make out!
The stars Merak and Dubhe form the pointers which will lead you to the Pole Star, and
hence find North. The stars Alcor and Mizar form a naked eye double which repays
observation in a small telescope as Mizar is then shown to be an easily resolved double
star. A fainter reddish star forms a triangle with Alcor and Mizar.
Ursa Major contains many interesting "deep sky" objects. The brightest, listed in
Messier's Catalogue, are shown on the chart, but there are many fainter galaxies in the
region too. In the upper right of the constellation are a pair of interacting
galaxies M81 and M82 shown in the image below. M82 is undergoing a major burst of
star formation and hence called a "starburst galaxy". They can be seen together using a
low power eyepiece on a small telescope.
M81 and M82
Another, and very beautiful, galaxy is M101 which looks rather like a pinwheel firework,
hence its other name the Pinwheel Galaxy. It was discovered in1781 and was a late
entry to Messier's calalogue of nebulous objects. It is a type Sc spiral galaxy seen face
on which is at a distance of about 24 million light years. Type Sc galaxies have a
relatively small nucleus and open spiral arms. With an overall diameter of 170,000 light
it is one of the largest spirals known (the Milky Way has a diameter of ~ 130,000 light
years).
M101 - The Ursa Major Pinwheel Galaxy
Though just outside the constellation boundary, M51 lies close to Alkaid, the leftmost
star of the Plough. Also called the Whirlpool Galaxy it is being deformed by the
passage of the smaller galaxy on the left. This is now gravitationally captured by M51
and the two will eventually merge. M51 lies at a distance of about 37 million light years
and was the first galaxy in which spiral arms were seen. It was discovered by Charles
Messier in 1773 and the spiral structure was observed by Lord Rosse in 1845 using the
72" reflector at Birr Castle in Ireland - for many years the largest telescope in the world.
M51 - The Whirlpool Galaxy
Lying close to Merak is the planetary nebula M97 which is usually called the Owl Nebula
due to its resemblance to an owl's face with two large eyes. It was first called this by
Lord Rosse who drew it in 1848 - as shown in the image below right. Planetary nebulae
ar the remnants of stars similar in size to our Sun. When all possible nuclear fusion
processes are complete, the central core collpses down into a "white dwarf" star and the
the outer parts of the star are blown off to form the surrounding nebula.
The constellation Hercules
Hercules
Between the constellation Bootes and the bright star Vega in Lyra lies the constellation
Hercules. The Red Giant star Alpha Herculis or Ras Algethi, its arabic name, is one of the
largest stars known, with a diameter of around 500 times that of our Sun. In common
with most giant stars it varies its size, changing in brightness as it does so from 3rd to
4th magnitude. Lying along one side of the "keystone" lies one of the wonders of the
skies, the great globular cluster, M13. Just visible to the unaided eye on a dark clear
night, it is easily seen through binoculars as a small ball of cotton wool about 1/3 the
diameter of the full Moon. The brightness increases towards the centre where the
concentration of stars is greatest. It is a most beautiful sight in a small telescope. It
contains around 300,000 stars in a region of space 100 light years across, and is the
brightest globular cluster that can be seen in the northern hemisphere.
The Globular Cluster M13 in Hercules. Image by Yuugi Kitahara
The constellation Virgo
Virgo
Virgo, in the south-east after sunset this month, is not one of the most prominent
constellations, containing only one bright star, Spica, but is one of the largest and is very
rewarding for those with "rich field" telescopes capable of seeing the many galaxies that
lie within its boundaries. Spica is, in fact, an exceedingly close double star with the two B
type stars orbiting each other every 4 days. Their total luminosity is 2000 times that of
our Sun. In the upper right hand quadrant of Virgo lies the centre of the Virgo Cluster of
galaxies. There are 13 galaxies in the Messier catalogue in this region, all of which can
be seen with a small telescope. The brightest is the giant elliptical galaxy, M87, with a
jet extending from its centre where there is almost certainly a massive black hole into
which dust and gas are falling. This releases great amounts of energy which powers
particles to reach speeds close to the speed of light forming the jet we see. M87 is also
called VIRGO A as it is a very strong radio source.
The Giant Elliptical Galaxy M87 HST image showing the jet
Below Porrima and to the right of Spica lies M104, an 8th magnitude spiral galaxy about
30 million light years away from us. Its spiral arms are edge on to us so in a small
telescope it appears as an elliptical galaxy. It is also known as the Sombrero Galaxy as it
looks like a wide brimmed hat in long exposure photographs.
The constellations Lyra and Cygnus
Lyra and Cygnus
This month the constellations Lyra and Cygnus are rising in the East as darkness falls
with their bright stars Vega, in Lyra, and Deneb, in Cygnus, making up the "summer
triangle" of bright stars with Altair in the constellation Aquila below. (see sky chart
above)
Lyra
Lyra is dominated by its brightest star Vega, the fifth brightest star in the sky. It is a
blue-white star having a magnitude of 0.03, and lies 26 light years away. It weighs three
times more than the Sun and is about 50 times brighter. It is thus burning up its nuclear
fuel at a greater rate than the Sun and so will shine for a correspondingly shorter time.
Vega is much younger than the Sun, perhaps only a few hundred million years old, and
is surrounded by a cold,dark disc of dust in which an embryonic solar system is being
formed!
There is a lovely double star called Epsilon Lyrae up and to the left of Vega. A pair of
binoculars will show them up easily - you might even see them both with your unaided
eye. In fact a telescope, provided the atmosphere is calm, shows that each of the two
stars that you can see is a double star as well so it is called the double double!
Epsilon Lyra - The Double Double
Between Beta and Gamma Lyra lies a beautiful object called the Ring Nebula. It is the
57th object in the Messier Catalogue and so is also called M57. Such objects are called
planetary nebulae as in a telescope they show a disc, rather like a planet. But in fact
they are the remnants of stars, similar to our Sun, that have come to the end of their life
and have blown off a shell of dust and gas around them. The Ring Nebula looks like a
greenish smoke ring in a small telescope, but is not as impressive as it is shown in
photographs in which you can also see the faint central "white dwarf" star which is the
core of the original star which has collapsed down to about the size of the Earth. Still
very hot this shines with a blue-white colour, but is cooling down and will eventually
become dark and invisible - a "black dwarf"! Do click on the image below to see the large
version – it’s wonderful!
M57 - the Ring Nebula
Image: Hubble Space telescope
M56 is an 8th magnitude Globular Cluster visible in binoculars roughly half way between
Alberio (the head of the Swan) and Gamma Lyrae. It is 33,000 light years away and has
a diameter of about 60 light years. It was first seen by Charles Messier in 1779 and
became the 56th entry into his catalogue.
M56 - Globular Cluster
Cygnus
Cygnus, the Swan, is sometimes called the "Northern Cross" as it has a distinctive cross
shape, but we normally think of it as a flying Swan. Deneb, the arabic word for "tail", is
a 1.3 magnitude star which marks the tail of the swan. It is nearly 2000 light years away
and appears so bright only because it gives out around 80,000 times as much light as
our Sun. In fact if Deneb where as close as the brightest star in the northern sky, Sirius,
it would appear as brilliant as the half moon and the sky would never be really dark
when it was above the horizon!
The star, Albireo, which marks the head of the Swan is much fainter, but a beautiful
sight in a small telescope. This shows that Albireo is made of two stars, amber and bluegreen, which provide a wonderful colour contrast. With magnitudes 3.1 and 5.1 they are
regarded as the most beautiful double star that can be seen in the sky.
Alberio: Diagram showing the colours and relative brightnesses
Cygnus lies along the line of the Milky Way, the disk of our own Galaxy, and provides a
wealth of stars and clusters to observe. Just to the left of the line joining Deneb and
Sadr, the star at the centre of the outstretched wings, you may, under very clear dark
skys, see a region which is darker than the surroundings. This is called the Cygnus Rift
and is caused by the obscuration of light from distant stars by a lane of dust in our local
spiral arm. the dust comes from elements such as carbon which have been built up in
stars and ejected into space in explosions that give rise to objects such as the planetary
nebula M57 described above.